Citrus juice concentrate method

ABSTRACT

A citrus juice concentrate processing homogenizes a mixture of citrus juice and pulp within or after a multi-effect, multi-stage evaporator. The homogenizer employs a positive displacement pump for pumping the citrus juice mixture through an orifice with a high pressure differential across the orifice. The homogenizer reduces viscosity of the citrus juice mixture. Inter-stage placement of the homogenizer further enables final citrus juice concentrate Brix levels of 72° Brix and greater to be achieved.

This is a continuation of co-pending application Ser. No. 07/399,171filed on Aug. 28, 1989, abandoned which is a continuation-in-part ofSer. No. 07/046,346 filed May 1, 1989, now U.S. Pat. No. 4,886,574.

BACKGROUND OF THE INVENTION

Most citrus juice beverages, such as orange juice, are derived from aconcentrate. Typically, juice and pulp extracted from various citrusfruits are processed through an evaporator system under vacuum whichevaporates liquid (i.e. water) contained in the juice and pulp mixture,and leaves a citrus juice product or concentrate. Liquid is evaporatedfrom the citrus juice concentrate until a 62° to 65° Brix level isachieved where Brix is the unit of percent sugar content of the citrusjuice concentrate. The 65° Brix citrus juice concentrate is then storedunder required refrigeration at about 20°-27° Fahrenheit to preventspoilage. There, the citrus juice concentrate congeals and forms afrozen juice concentrate. The frozen concentrate is sold to dispensingbusinesses who dilute the concentrate to a 12° Brix beverage, packagethe beverage and distribute the beverage to industries such asrestaurants and hospitals for bulk consumption, or to retail stores forindividual consumer sale. Or the frozen concentrate is diluted to 42°Brix for commercial sale in frozen form which is subsequently diluted bypurchasing consumers to about a 12° Brix juice beverage.

Besides varietal differences, juices differ due to weather (freezing)and other growing conditions. A proper mixture of fruit varieties andmaturities must be used to obtain an acceptable color, Brix level andviscosity of the concentrate. While a higher final Brix level isdesirable for reducing storage and transportation expenses of theconcentrate, a low viscosity level is desirable to decrease difficultyin the pumping of the concentrate through the evaporator system and intoand out of storage.

Several complications exist in this process. For example, throughout theevaporation process, the citrus juice concentrate becomes more viscous.Toward the end of the evaporation process, scorching or burn on andproduct build-up of the concentrate may occur due to reduced andinconsistent flow of the viscous concentrate. Such scorching is highlydetectable in the taste of the finished product and requires cleaning ofthe evaporator. Hence, the achievement of higher Brix levels is limitedby the viscosity of the concentrate.

Another problem concerns the storing and transporting of theconcentrate. Large capacity freezers and refrigerated trucks at theproper temperature must be used due to the volume of space andtemperature required by the juice concentrate.

Several methods of blending different varieties of juice and/or pulphave been used to address the problem of obtaining concentrate of a highBrix level and low viscosity. However, due to unpredictable weatherconditions, different varieties and maturities of fruits may be producedfrom one crop to the next and from one season to the next. Thus, adifferent method of blending must be devised for each crop.

A centrifuge has been used to remove pulp and thus decrease viscosity ofthe initial juice and pulp where a change in season, maturity andvariety (i.e. different cultivars and early to late season fruit)produces fruit with relatively more pulp. The centrifuge, however,causes the loss of two to three percent of the useable fruit product.

Various enzymes have also been suggested to enhance Brix level whilemaintaining a suitable viscosity level of the concentrate, but enzymesrequire the introduction of a foreign material to the juice which is notpermitted under Federal Standard of Identity Regulations.

SUMMARY OF THE INVENTION

The present invention discloses a system for forming juice concentratewhich reduces the viscosity of the juice concentrate produced by theevaporation of liquid from a supply of juice. The reduction of viscosityof the juice concentrate prior to storage facilitates the handling ofthe concentrate. Further, the present invention enables the reduction ofviscosity in the juice concentrate in an intermediate step within theevaporation process. Such reduction of viscosity aids in the flow ofjuice concentrate through the evaporation system to prevent scorching ofthe juice concentrate and build-up of the product with resulting damageto the tube walls, and thus allows a more constant evaporator output of65° Brix or higher and preferably Brix levels of greater than about 72°Brix to be achieved. Juice concentrate of such higher Brix levelsenables storage and shipment at decreased volumes and at temperaturesaround about 40° F.

A system embodying the present invention comprises an evaporator ofseveral stages and a homogenizer connected to the output of one of theevaporator stages. Liquid (i.e. water) from a supply of juice isevaporated in each stage of the evaporator to form a juice concentrate.After flowing through the stage to which the homogenizer is connected,the juice concentrate is homogenized to form a juice concentrate whichis decreased in viscosity. Liquid from the homogenized juice concentrateis evaporated in any remaining stages of the evaporator, and the finaljuice concentrate is stored under the requisite refrigeration dependingon the final Brix level achieved. The closer the homogenizer is to thelast stage of the evaporator, the greater may be the decrease inviscosity.

In a preferred embodiment, citrus juice and pulp, such as that fromoranges, are processed through a first part of an evaporator, thenhomogenized, and processed in a second part of the evaporator to achievean increased Brix level of about 65° Brix or higher and preferably about72° Brix.

In addition, the citrus juice and pulp may be preheated before beingpassed through the evaporator.

In accordance with one aspect of the present invention, the homogenizeris preferably a positive displacement plunger pump which pumps juiceconcentrate through an orifice with a pressure differential across theorifice of at least 500 psi. In a preferred embodiment the orifice is aknife-edge type valve.

In accordance with another aspect of the present invention, amulti-effect, multi-stage evaporator is used to evaporate liquid fromthe juice concentrate. In a preferred embodiment, the homogenizer isconnected just prior to the last effect of a thermally accelerated shorttime evaporator (TASTE) in which juice concentrate is passed in heatexchange relationship with steam.

BRIEF DESCRIPTION OF THE DRAWING

The foregoing and other objects, features and advantages of theinvention will be apparent from the following more particulardescription of a preferred embodiment of the invention, as illustratedin the accompanying drawing. The drawing is not necessarily to scale,emphasis instead being placed upon illustrating the principles of theinvention.

FIG. 1 is a schematic of a preferred embodiment of the presentinvention.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT

A schematic diagram of a citrus juice concentrate processor embodyingthe present invention is provided in FIG. 1. Dashed lines indicate theflow path of steam from a source 14 and solid lines indicate the flowpath of the citrus juice mixture being processed. Four "Effects" of thesystem 12 are defined by the four positions at which steam is introducedto the evaporator 16 and are labeled I, II, III, and IV. Each Effectcomprises a stage or stages 10, 20, 30, 40, 50, 60 which serve as heatexchangers, as will be discussed. Evaporator 16 is preferably of thethermally accelerated short time evaporator type.

A mixture of juice and pulp from citrus fruit is introduced to theprocessor 12 through juice inlet line 78 which enters preheater 18, thefirst preheater of a series of preheaters. The citrus juice mixture iswarmed in preheater 18, passed to succeeding preheaters, 22, 24, 26which are positioned between the four Effects, one preheater at eachintermediate position, and lastly passed to a fifth preheater 28positioned near the head of Effect I.

Preheater 28 is supplied with steam by steam inlet line 32. Each of theintermediate preheaters 22, 24, 26 receives steam from an outlet of therespective preceding Effect. That is, steam outlet line 44 of Effect Iprovides steam for preheater 26. Steam outlet line 46 of Effect IIprovided steam for preheater 24. Steam outlet line 48 of Effect IIIprovides steam for preheater 22. Preheater 18 receives steam outputtedfrom Effect IV and subsequently transfers the steam to cooling watertank 92 through steam outlet line 58. Each preheater uses therespectively provided steam to heat the citrus juice mixture beforepassing the juice mixture to a succeeding preheater.

The citrus juice mixture is at a final preheated temperature of about210° F. and at a concentration of about 12° Brix after passing throughthe last preheater of the series, preheater 28. The preheated citrusjuice mixture is then carried to and enters Effect I through line 62.Effect I is supplied with the steam from preheater 28 through steam line42. In Effect I, the citrus juice mixture is passed in heat exchangerelation with the steam. This is accomplished with tubular stage 10,which comprises inner cylinders coaxially positioned within an outercylinder. The citrus juice mixture is passed along the inner cylindersat the same time steam is passed through the outer cylinder. Water inthe citrus juice mixture is evaporated off, leaving a relatively moreviscous citrus juice mixture.

A vapor separator 70 at the bottom of the coaxial cylinders separatesthe water vapor from the citrus juice mixture. The water vapor mixedwith the steam is transferred through steam outlet line 44 of vaporseparator 70 to preheater 26 as previously mentioned. Transfer pump 64pumps the citrus juice mixture from vapor separator 70 to the head oftubular stage 20 of Effect II. At this point, the citrus juice mixtureis about 18° Brix at about 180° to about 190° F.

Water from the citrus juice mixture is evaporated in tubular stage 20 ofEffect II in the same manner as in tubular stage 10 of Effect I, butwith preheater 26 supplying the steam to tubular stage 20 through steamline 56. Vapor separator 72 at the bottom of tubular stage 20 separatesthe newly evaporated water vapor from the citrus juice mixture furtherincreasing viscosity of the mixture. The vapor is transferred throughsteam outlet line 46 to preheater 24 and transfer pump 66 pumps theincreased viscosity citrus juice mixture to the head of tubular stage 30of Effect III. The citrus juice mixture enters stage 30 at about a 28°Brix concentration at about 140° F.

Preheater 24 supplies steam to tubular stage 30 through steam line 54.Water from the citrus juice mixture is further evaporated in tubularstage 30. The collected vapor and viscous citrus juice mixture areseparated in vapor separator 74 at the bottom end of stage 30. The watervapor is transferred through steam outlet line 48 to pre-heater 22 andsubsequently to tubular stages 40, 50, 60 of Effect IV through steamline 52. Transfer pump 68 pumps the three-stage processed viscous citrusjuice mixture into homogenizer 90.

Homogenizer 90 includes a positive displacement plunger pump whichproduces a constant output flow independent of operating pressure.Homogenizer 90 pumps the citrus juice mixture through an orifice 98 witha high pressure differential across the orifice 98 of about 500 psi andgreater. It is preferred that the pressure differential across theorifice 98 be about 2300 psi to about 5000 psi. For example, an orificeof a knife edge type valve is suitable.

Further, homogenizer 90 is set to match the flow rate of evaporator 16.This is accomplished by homogenizer 90 having an output flow rate setequal to the maximum incoming flow rate from evaporator 16, and byhaving a feedback bypass 94 which compensates for the lack of input flowduring minimum incoming flow from evaporator 16.

The homogenized citrus juice mixture is at a concentration of about 40°Brix and at a temperature of about 115° F. Homogenizer 90 pumps thehomogenized citrus juice mixture into tubular stage 40, the first ofthree tubular stages in Effect IV (the remaining part of themultiple-effect, multiple-stage evaporator 16). Evaporation of waterfrom the citrus juice mixture takes place in each of the three tubularstages 40, 50, 60 of Effect IV in the same manner as in the previoustubular stages. The citrus juice mixture becomes more viscous after eachstage. Tubular stages 40, 50, 60 share the steam inputted to Effect IVthrough steam line 52 from preheater 22. Each of the tubular stages 40,50, 60 is respectively connected to a vapor separator 76, 86, 88. Vaporseparator 76 passes collected water vapor to stage 50 and passes theprocessed citrus juice mixture to transfer pump 80, which transfers themixture to the head of tubular stage 50. Vapor separator 86 at thebottom end of tubular stage 50 passes collected vapor to stage 60 andpasses the processed citrus juice mixture to transfer pump 82 whichtransfers the juice mixture to the head of tubular stage 60. Vaporseparator 88, at the bottom end of tubular stage 60 passes collectedvapor to preheater 18 and passes the processed citrus juice mixture totransfer pump 84 which pumps the citrus juice mixture out of the systemin concentrate form at about 65° Brix to about 75° Brix.

Because tubular stages 40, 50 and 60 share in succession the sameworking steam, tubular stages 50 operates at a cooler temperature thanstage 40 and tubular stage 60 operates at a cooler stage than stage 50.Hence, the citrus juice mixture is cooled at each of the tubular stages40 50 and 60. The output temperature of the citrus juice concentrate isabout 60° F.

The intereffect arrangement of preheaters 18, 22, 24, 26 and 28 allowsfor increased utilization of energy. However, preheater 28 could havebeen used alone with juice inlet line 78 leading directly to preheater28 and with vapor separator 88 of the last stage 60 directly passingvapor to cooling water tank 92.

It is understood that the evaporator 16 of the present invention may beone of various designs of multiple effect, multiple stage evaporatorsystems with and without intereffect preheaters, or with interstagepreheaters plus a condensate recovery scheme as discussed in "CitrusEvaporator Technology" by C. S. Chen in Transactions, Vol. 25, no. 5, pp1457-1463, 1982, and herein incorporated by reference.

It is also understood that one or more homogenizers 90 can be positionedafter any transfer pump to decrease viscosity of the citrus juicemixture, which in turn provides a more uniformly flowing citrus juicemixture within the system. Such uniform flow is typically most desirablein the last Effect IV where the citrus juice mixture typically becomesso viscous that scorching and build-up may occur. In some cases, thecloser the homogenizer is positioned to the last tubular stage 60, thegreater is the reduction in viscosity of the citrus juice mixture. Thus,the viscosity of the citrus product decreases in an amount defined as afunction of position of the homogenizer with respect to the evaporator.

Furthermore, intereffect or interstage homogenization reduces viscositysuch that further evaporation may be possible which enables a higherpercent sugar content (Brix level) to be achieved. At Brix levels at orabove 72° Brix, bacteria which causes spoilage are inactive. Theintereffect homogenization of the embodiment of FIG. 1 may allow forproduction of a citrus juice concentrate with about a 75° Brixconcentration level which can be stored at freezing temperatures ofabout 40° F.

In a system where scorching is not a problem and a homogenizer 96 ispositioned after the last transfer pump 84, a reduction in viscosity isalso achieved. This is most important when producing a product of 72°Brix or higher. However, a Brix level above 65° is not necessarilyachieved because the viscosity in the final effect is too high to allowsufficient evaporation. Hence, an optimum position of the homogenizer isbetween the last two Effects, Effects III and IV, after transfer pump68, where both high reduction in viscosity and increase in Brix level isobtained. Depending on the tendency to scorch within Effect IV and theaccessibility of pumps 80 and 82, other potential optimum positions ofthe homogenizer are between stages 40 and 50 or between stages 50 and60.

It is further noted that homogenizers 90 and 96 reduce the viscosity ofthe citrus juice mixture with no product loss in contrast to acentrifuge which typically causes the loss of 2% to 3% of the juiceproduct.

The citrus juice mixture referred to throughout this discussion is meantto include, but not to be limited to, juice from citrus fruits such asoranges, grapefruits, lemons and limes; and also other fruits such aspineapples, passion fruit, guava, and papaya, to name a few. The presentinvention processes these juices with or without pulp. Other juices maybe similarly processed by the present invention to form a high Brixlevel juice concentrate.

Further benefits of the present invention include the following. Theevaporator 16 operates much more smoothly when at least homogenizer 90is connected to it. This is noticeable in all the stages 40, 50, 60after the homogenizer 90. Operators can better control the output of theevaporator 16 without continuous adjustments being required to steam andflow of infeed juice.

Further the homogenizers 90, 96 completely and consistently eliminatedefects in the finished concentrate. Defects are formed from flakes ofHesperidin which, having accumulated on the sides of the tube bundles ofthe stages, start to break off and show up in the end concentrateproduct. The homogenizers 90, 96 break these flakes into particles of asize which makes them no longer noticeable in the finished product. Thisis important for two reasons. First, the concentrate designated to besold on the futures market has to obtain a specific score on severalpredesignated criteria such as color, Brix, taste, acid, defects, etc.The optimal score for the defects criteria is 20. If defects arenoticed, a score of only 19 or 18 may be achieved and the lost pointswill have to be recouped with extra color or other characteristics, eachof which will cost. Hence by eliminating defects, the present inventionsaves cost in the processing of juice concentrate for the futuresmarket. The second reason why homogenizer breakage of flakes (defects)is important relates to down time for cleaning the evaporator to preventdefects from initially occurring. With the homogenizers 90, 96 of thepresent invention able to eliminate defects by substantially reducingthe size of flakes, the evaporator 16 can be allowed to runsignificantly longer between cleaning shutdowns. Lost production andenergy costs required to bring the evaporator 16 back up to fulloperation are thus avoided.

Another major benefit of the present invention is the reduction ofbottom pulp by 1-11/2%. This is translated to increased yield of thesame amount.

Because the present invention enables viscosity of the concentrate to bereduced in processing, an increase in Brix level to 72°-75° is alsoenabled. It is noted that the concentrate product tends to gel at suchhigh Brix levels, but the Applicant has overcome the gelling by usingshear on the concentrate product as it leaves the evaporator 16. Onceshear has been applied, the gel formations do not form and theconcentrate product remains as a pumpable liquid in storage.

Shear is applied to the concentrate by a shearing device coupled to theend of evaporator 16. The shearing device may be a homogenizer, beater,or positive displacement pump. One such pump is a low energy, shearingpump known as a lobe pump. It is noted that a homogenizer tends toprovide more shear than necessary.

Additional benefits of note include a reduction or elimination of theuse of centrifuges to reduce viscosity of the infeed juice. Generally,such centrifuges lose or decrease yield. Also, there is a reduction ofdependence on juice from certain varieties which are blended withconcentrate product as a means of reducing viscosity. In addition, theincreased concentration obtained with the present invention allows theuse of a 5 to 1 dispenser pack instead of a 4 to 1 dispenser pack. Thissaves in shipping and storage costs.

While the invention has been particularly shown and described withreference to a preferred embodiment thereof, it will be understood bythose skilled in the art that various changes in form and details may bemade therein without departing from the spirit and scope of theinvention as defined by the appended claims.

I claim:
 1. A method of processing citrus juice concentrate in aninterrelated homogenization and evaporation steps, the stepscomprising:providing citrus juice which decreases in viscosity withhomogenization and has a tendency to gel at brix levels of about 72° toabout 75°; in an evaporator, evaporating the citrus juice preheated to afinal temperature of about 210° F. in a multistage, multieffectevaporator to form a viscous citrus product; and decreasing viscosity ofthe citrus product in an amount defined as a function of position of ahomogenizer with respect to the evaporator, said decreasing viscosityincluding homogenizing the viscous citrus product at one of anintermediate position and output end of the multistage, multieffectevaporator, said homogenizing at one of an intermediate position andoutput end of the evaporator further aiding flow throughout theevaporator by providing uniform flow of the citrus product throughoutthe evaporator.
 2. A method as claimed in claim 1 wherein the step ofevaporating citrus juice includes passing the citrus juice in heatexchange with a heat source to evaporate liquid from the citrus juiceand form a citrus juice concentrate.
 3. A method as claimed in claim 1wherein the step of evaporating citrus juice includes passing the citrusjuice through a thermally accelerated short time evaporator.
 4. A methodas claimed in claim 1 wherein the step of homogenizing the viscouscitrus product includes pumping the citrus product through an orificewith a pressure differential across the orifice of at least 500 psi. 5.A method as claimed in claim 1 wherein the step of homogenizing includesreducing defects in the citrus product.
 6. A method as claimed in claim1 wherein the step of homogenizing includes reducing bottom pulp in thecitrus product.
 7. A method of increasing the Brix level of citrus juiceconcentrate in an interrelated homogenization and evaporation steps, thesteps comprising:providing citrus juice which decreases in viscositywith homogenization and has a tendency to gel at Brix levels of about72° to about 75°; in an evaporator:(a) evaporating liquid from citrusjuice preheated to a final temperature of about 210° F. in a multistage,multieffect evaporator to form a citrus juice concentrate; (b)positioning a homogenizer between last two effects of the evaporator;(c) reducing viscosity of the citrus juice concentrate by homogenizingthe citrus juice concentrate in said homogenizer; and (d) furtherevaporating liquid from the homogenized citrus juice concentrate,wherein the step of evaporating liquid from citrus juice includespassing the citrus juice through a first part of a multiple-effectmultiple-stage evaporator, and the step of further evaporating liquidincludes passing the citrus juice concentrate through a remaining partof said multiple-effect multiple-stage evaporator, said steps ofevaporating and further evaporating providing an evaporation processwithin which the step of homogenizing is performed to aid flowthroughout the evaporation process.
 8. A method as claimed in claim 7wherein the step of further evaporating includes providing a citrusjuice concentrate increased in concentration such that a subsequent 5 to1 dispensing is enabled.